As an interest on an environment gradually increases in recent years, a demand has existed for the development of a small-size sensor capable of accurately obtaining different kinds of information within a short period of time. Particularly, for the purpose of making a residential space pleasant, coping with a harmful industrial environment and managing a production process of beverage and foodstuff, efforts have been made to achieve the size reduction, precision enhancement and price reduction of a micro multi-array sensor such as a gas sensor for easily measuring a gas concentration or the like.
The currently available gas sensor gradually evolves from a ceramic-sintered gas sensor or a thick-film-type gas sensor to a micro gas sensor having the form of a micro electro mechanical system (MEMS) due to the application of a semiconductor process technique.
From the viewpoint of a measurement method, a method of measuring a change in the electric characteristics of a sensing material of a sensor when a gas is adsorbed to the sensing material is most frequently used in the currently available gas sensor. Typically, a metal oxide such as SnO2 or the like is used as the sensing material to measure a change in the electrical conductivity depending on the concentration of a measurement target gas. This measurement method has an advantage in that it is relatively easy to use the method. A change in the measurement value becomes conspicuous when the metal oxide sensing material is heated to and operated at a high temperature. Accordingly, accurate temperature control is essential in order to rapidly and accurately measure a gas concentration. Furthermore, the gas concentration is measured after the sensing material is reset or restored to an initial state by forcibly removing gas species or moisture already adsorbed to the sensing material through high-temperature heating.
However, such a conventional sensor is configured to detect one kind of gas. In order to detect plural kinds of gases, there is a need to provide several sensors. This poses a problem in that the volume grows larger and the power consumption increases.